Furnace and control therefor



March 21, 1939. L. v. PITTMAN ET AL 2,151,439

FURNACE AND CONTROL THEREFOR Filed Aug. 26, 1936 '7 Shee'ts-Sheet 1RocKmG CENTER SELE CTO R March 21, 1939. L v PITTMAN ET AL FURNACE ANDCONTROL THEREFOR Filed Aug. 26, 1936 7 Sheet s-Sheet 2 M ED EH5 lea/2 77#1127 awn/Q7: Web '78 Award K March 21, 1939. 1.. v PITTMAN ET ALFURNACE AND CONTROL THEREFOR Filed Aug. 26, 1956 '7 Sheets-Sheet 4 March21, 1939. v. PITTMAN ET AL FURNACE AND CONTROL THEREFOR Filed Aug. 26,1936 7 Shee'ts-Sheet 5 MINUTES ME U 5 lean? 7% man.

March, 21, 1939. L. v. PITTMAN ET AL 2,151,439

FURNACE AND CONTROL THEREFOR Filed Aug. 26, 1936 'r Sheets-Sheet 6 March21, 1939. Lv v PITTMAN ET AL FURNACE AND CONTROL THEREFOR Filed Aug. 26,1936 7 Sheets-Sheet '7 uxu Patented Mar. 21, 1939 UNITEDQI'STATES PATENTOFFICE FURNACE AND CONTROL THEREFOR Application August 2c, 1930, SerialNo. 97,932

28 Claims.

The present invention relates generally to a furnace for melting ofmetals, and more particularly to improvements in control means for suchdevices of the type wherein the melting chamber is rotated or rockedduring the melting operation.

Attempts have been made in the past to produce suitable mechanisms forcontrolling the rocking cycles of such furnaces, so as to obtain thebest results under varied conditions of operation. These mechanisms haveembodied mechanical, electrical and combination mechanicalelectricalarrangements, but as far as we have knowledge, these attempts havefailed to produce a control mechanism of sufiicient flexibility topermit wide variations in the rocking cycle in a quick and easy manner.

In the operation of furnaces of the hereindescribed type, it has beenfound that the best results are obtained when the angle of rock" or 20rocking range" is the greatest possible without damage to theelectrodes. In order to maintain such condition it will be apparent thatthis angle of rock will not be the same during different parts of themelting cycle. During the earlier part of the melting cycle, the roof ofthe melting chamber is at higher temperature than the hearth,

which is protected by the charge. As the surfaces of the charge becomesoftened, they tend to adhere and thus prohibit tumbling which might 30damage the electrodes. The rocking angle might therefore be increased asthe melting progresses.

A gradually increasing volume of metal becomes molten and washes backand forth over the lining surface of the melting chamber and thatportionof the charge which has not been melted.

As the rocking proceeds, the molten metal absorbs additional heat fromthe higher temperature lining and carries it to the unmelted charge,

thus introducing heat into the metal which would otherwise be wasted.

It will be apparent therefore that at the beginning of the meltingcycle, depending upon the melting characteristics of the metalscomposing the charge, it might be desirable to maintain the rockingangle at a small constant value for a predetermined interval of timebefore starting to increase the rocking angle, or it might be desirableto begin the operation with a very small rock having a very small rateof increase. In either case, after a given interval the angle of rockand its rate of change may be increased.

Consequently, it therefore follows that for securing the best results,the angle of rock should be increased at substantially the same rate asthe rate at which the charge of metal is being melted.

The complete rocking cycles for charges of different metals maytherefore vary greatly in their characteristics such as, for example,the length of rocking time, the amount of the angle of rock at differentperiods of the cycle, the rate of increase of the angle of rock atdifferent portions of the cycle, etc.

It is therefore a primary object of the present invention to providecontrol mechanisms which will enable selective adjustment of theconstant and variable characteristics of the various ele ments of therocking cycle to give a desired cycle of operation, and which willpermit a presetting of the control mechanism so that once the rocking isstarted, the pre-determined cycle will be automatically carried outwithout further attention from the operator. Incident to this object ofour invention are numerous other objects, the attainment of whichcontributes materially to the achievement of the primary object.Theseobjects appear more fully in the accompanying specification, andinclude the following:

(1) To provide improved means for normally preventing rocking of themelting chamber in a forward or reverse direction beyond safe limits.

(2) To provide improved protective means for stopping the rockingoperation in the case of an abnormal condition of operation, which wouldcause the melting chamber to travel in a forward or reverse directionpast the safe maximum angle of rock limits.

(3) To provide improved means for controlling the rate of increase ofthe rocking angle.

(4) To provide push button control for manually augmenting the automaticoperation of the 5 furnace.

(5) To provide jogging push button control for moving the meltingchamber during the pouring operation.

(6) To provide improved index for indicating the center of the rockingangle.

(7) To provide improved mechanism for automatically controlling theamount of increase of the rocking angle.

(8) To provide a limit switch mechanism having an actuating member whichis adapted upon predetermined initial movement in opposite directionsfrom a normal position to respectively operate a set of controlcontacts, and which will upon further movement in either directionoperate a third common set of contacts.

(9) To provide automatic means whereby the melting chamber may beinitially rocked through a selected constant rocking angle for apredetermined period of time, after which the angle of u rock will beprogressively increased for a subse quent predetermined period of timeat a varying rate.

In accordance with the general features of the invention, it is proposedto provide a pair of control cams, one of which is oscillated inaccordance with the oscillatory movements of the furnace, and the otherof which is driven by a timing motor through a variable speedconnection. The first of these cams is substantially heart shaped and isarranged-to alternately actuate in its oscillatory movement a pair ofswitches for normal- 1y controlling the direction of movement of thefurnace.

These control switches are mounted on a pivotally supported arm. wherebymovement oi the arm will vary the distance of the switches relativetothe associated cam surface with the result that it will be necessary forthe cam to oscillate a greater distance before the switches are actuated. In other words, movement of the pivoted arm will cause a variationin the angle through which the melting chamber is rocked. Moreover, therate of increase in the rocking angle will be in accordance with thespeed of movement of the pivoted arm.

The second cam is therefore utilized to control the movement of thepivoted arm, and a cam surface is selected for this cairn of such pitch.as to give the desired increases in the amounts oi? the rocking angles.

By driving the t speed, the length in cycle will be completed may timeinterval required to oroi, termined minimum value of mined maximum valueof rock It will also be evident that by disconnecting the timing motorso that the second cam is not actuated, and by setting the second cam atany position in its course of movement, a constant rocking at the angledetermined thereby will resuit.

Also, by providing a lost motion connection between the timing motor andthe second cam, which connection is adjustable so as to necessitaterunning of the timing motor for different periods of time before the cambegins to operate, it is possible to rock the chamber at a selectedconstant angle of rock for the selected period of time before the cambegins to move and increase the angle of rock for the balance of therocking cycle.

An additional feature of the invention resides in the provision of camactuated control switches which are arranged to be operated by camssupported on the chamber. These control switches are so connected withthe normal control mechanism that whenever the normal control operatesto cause the chamber rock to reach the maximum safe rocking anglelimits, the cam actuated switches associated directly with the chamberwill be operated to supersede the normal control and continue therocking movement at the maximum angle of rock.

The cam and switches which are actuated in response to the directmovement of the chamber are further arranged so that if the chamberduring abnormal operation should tend to move past the safe angle ofrock limit, then the switches are actuated to stop the chamber operatingmechanism.

A still further feature resides in the provision of push button controlequipment which may be used to supplement the automatic control mechii.it to a predeteranism, for operating the chamber so that it may be movedin any desired direction, as for locating the charging door of thechamber during the charging operation or for Jogging the chamber duringthe pouring operation. 5

Other objects and features of the invention will more fully appear fromthe following detailed description taken in connection with theaccompanying drawings which illustrate a single embodiment thereof, andin which: 10

Figure 1 is an end view of a furnace and control therefor embodying thefeatures of the herein described invention;

Figure 2 is an enlarged fragmentary plan view of the main controlmechanism, showing its connection to the furnace;

Figure 3 is an enlarged sectional View through the main controlmechanism to show the coop-- crative relationship of its internal parts,talten substantially on line III-III of Figure 21;

Figure 4 is an enlarged sectional view through the main controlmechanism to show the details of the driving connection from the furnacevariable speed driving connection with the tirning motor, takensubstantially on line Ilk -IV 2r of Figure 3;

Figure 5 is a partial sectional view, with parts shown in elevation, toshow the driving connection between the timing motor and the main control mechanism, taken substantially on line V "V of Figure 3;

F ii

ii: mentary sectional view through the main control mechanism showingthe details of the cam arrangement for controlling the rocking angle andincrease of the rocking angle, taken substantially on line VII-VII ofFigure 3;

Figure 8 is a view in elevation of the selector for varying the speed ofthe timing motor drive;

Figure 9 is a view in elevation of the maximum rock and over travellimit switch, the cover being removed to show the details of itsinterior mechamsm;

Figure 10 is a sectional view of the same, taken substantially on lineX-X of Figure 9;

Figure 11 is a partial sectional view showing further details of thelimit switch, taken on line XI-XI of Figure 9;

Figure 12 is a view diagrammatically showing the electrical andmechanical elements of the invention together with the inter-connectingelectrical control circuits; and

Figure 13 is a graphical representation of typical rocking cycles whichmay be attained with the present invention.

General description Illustrative of the present invention, there isshown in Figure 1 a furnace of the rocking type to which the hereindescribed novel control has been applied. Although the control equipmenthas been described herein in connection with an electric furnace, itwill be evident to one skilled in the art that the control equipment maybe with equal facility applied to any other device of a similar nature.

The rocking furnace embodies a melting chamber ii of cylindrical form,this chamber being provided with longitudinally spaced rails I6extending circumferentially around the shell which defines the chamber.These rails are adapted to I be supported on spaced rollers I80.rotatably mounted in suitable bearings in a supporting base structurel1.

The melting chamber is rocked back and forth by means of a main drivingmotor l8 which is connected through suitable speed reduction gearscontained in the gear housing as shown at l8. It is preferred to use adriving motor which may be electrically reversed, and, in the presentinstance, the motor is disclosed as being of the polyphase type whichmay be reversed simply by changing the phase connections of the motor.

Any suitable form of driving connection such as a pinion and gearconnection may be used for connecting the motor to the shell definingthe melting chamber.

The shell is provided with a pouring spout 28 which determines the safemaximum rocking angle of the chamber. In other words, it is notdesirable to rock the chamber through an angle which would cause themolten metal to wash past the entrance of the pouring spout. Althoughnot shown, the furnace is provided with suitable electrodes which aremounted in each end of the furnace chamber and are in axial alignment atthe center of rotation of the chamber.

All parts of the control equipment which are arranged to be adjusted andmanually operated by the operator of the furnace are contained in a maincontrol unit which is generally indicated at A.

The main control unit is located at one end of the furnace and in such aposition that the operator may have an unobstructed view so that thefurnace may be properly controlled during the pouring and chargingoperations, and in adjusting the control equipment to secure differentrocking cycles.

The main control unit is provided with control knobs which may bemanipulated by the operator and adjusted to give any type of rockingcycle desired. Not only does the operator have complete control of theangles through which the chamber may be rocked, but adjustments areprovided so that it is possible to increase the angle of rock at apredetermined rate. Moreover, selector means are provided so that thetime interval of the rocking cycle may be increased arid decreased asdesired. The electrical control for turning the automatic rockingmechanism on and off is conveniently mounted for manipulation by theoperator, and manual push button control is also placed so as to bewithin easy reach of the operator.

' Main rocking control mechanism The main rocking control mechanism iscontained in a box-like housing 2| which is supported at one end bymeans of a flanged fitting 22 connected at one end to the housing as bybolts 23 and at its other end forms a part of the bearing support forone of the wheels or rollers as shown at |6a upon which the chamber isrotatably supported.

The bottom portion of the housing is formed by a pan or cover 24 whichis removably held in position by a thumb nut 25. The upper surface ofthe housing has disposed thereon the various control elements foradjusting the different characteristics of the rocking cycle.

The rocking movement of the melting chamber is transmitted from thewheel or roller |6a associated with the main control unit, through ashaft connection 26, as shown in Figure 4, this shaft being rotatablysupported in the bracket fitting 22.

Mounted on the shaft 28 is aworm 21 which meshes with a worm wheel 28.The worm wheel 281s secured at one end of a rotatably mounted sleeve 29having its associated end rotatably supported in a bearing 30. The wormwheel is secured to a peripheral flange 3| on the sleeve as by rivets32. The other end of the sleeve is threaded to receive a nut 33 by meansof which an internal ring gear 34 is secured to this end of the sleeve.Between the worm wheel 28 and the internal ring gear 34, the sleeve isrotatably supported in an anti-friction bearing 35.

A shaft 36 extends through the sleeve 29 and is rotatably supportedtherein. One end of this shaft is contracted as shown at 31 to form ashoulder 38 for abutment by a gear 39 which is held onto the contractedportion by means of a nut 48. The teeth of the gear 39 mesh with theinternally disposed teeth of ring gear 34.

The opposite end of the shaft 36 projects through a cam compartment 4|and through the forward side of the main control unit housing.

Secured to the shaft 36 for rotation therewith is a cam member 42 havinga socket 43 on its back side surrounding the shaft for receiving one endof an expansion spring 44. The other end of this spring bears againstthe adjacent end of the sleeve 29. It will be apparent that with thisarrangement, the spring 44 tends to axially move the shaft 36 in such adirection as to retain the gear 38 in mesh with the teeth of gear 34,but that by pushing the shaft 36 in the opposite direction, these twogears may be disengaged. This disengaging movement of shaft 36 islimited by an abutment pad 45 which is formed in the housing adjacentthe nut 48.

By depressing a knob 46, the gears 33 and 34 may be moved out by meshingengagement and the position of cam 42 may be adjusted. Releasing theknob 46, the gears 34 and 38 are restored to meshing engagement.

As shown in Figure 7, it will be observed that the cam 42 issubstantially heart shaped having a plain cam surface 41 at its shortestradius.

cooperatively associated with the cam 42 is a T-shaped arm 48 which ismounted for pivotal movement about a pivot pin 49. The respective legsof this member are shown at 58, 5|, and 52. r

The long leg 58 carries a pair of switches 53 and 54, these switchesbeing secured to the arm as by suitable screws 55. These switches may beof circuit closing or opening type and are each provided with anactuating pin or button 56 which will actuate the associated switch whenit is depressed.

A pair of oppositely extending resilient fingers 51 and 58 are anchoredat their outer ends as shown at 59 and 60 to the leg 50. The free endsof these fingers are provided with cylindrical bearing members 6| whichare adapted to bear against the surface of the cam 42 and normallyproject slightly past a cam abutment surface 6|a on the leg 50. The arm48 is normally actuated in a counter-clockwise direction by the actionof a tension spring 62 having one end anchored as at 63 to a portion ofthe housing, and its other end 64 secured to the leg 5| of the arm.

From the foregoing description it will be ap-- parent that if theswitches 53 and 54 are so chosen so as to respectively control thereversing movement of the melting chamber, and since the cam 42 will berocked in accordance with the movement of the chamber,-the cam willalternately actuate the switches 53 and I4 and control the alternaterocking movement of the chamber. Moreover, it the arm 48 is moved in aclockwise direction so that the switch assembly just described is movedaway from the cam surface, greater amounts or rocking movement of thecam 42 will be necessary to actuate the control switches. A ready meansis therefore provided for adjusting the amount of rock of the meltingchamber.

When operating the control by means of push buttons, as will bedescribed later, the switches 53 and 54 are ineffective and the cam 42may be rotated past the points at which these switches would beactuated. As the cam 42 is rotated the members 51 and 58 are onlydeflected until the cam abutment surface Bla is engaged, whereupon themember 48 is shifted. With this arrange ment damaging forces areprevented from being applied by the cam to the switches or actuatingresilient fingers.

During the rocking movement of the melting chamber, the knob 46 willduplicate this rocking movement and by the provision of a pointer 55 onthe knob and an index mark 66 on the face of the housing, it is possiblefor the operator at all times to note the movement of the furnace bywatching the movement of the knob 46.

Also, the knob 46 provides means for manually adjusting the cam 42 inrelation to the bearing members 6|, so that the center oi the angle ofrock may in fact :madc t. col wl .he charging posit. at tho meltinclamber.

It will ofcoui. be apparent that the charging position of the meltingchamber is a. "variable and this charging position may be at any pointwithin the limits of the safe rocking angle of the melting chamber. Forexample, if the charging opening is disposed at the uppermost point onthe vertical center line through the chamber, then the operator coulddepress the knob 46 and rotate the cam member to rocking centerposition, at which position the pointer 65 on the knob will coincidewith the index mark 56. The rocking movement of the chamber will then bein forward and reverse direction on either side of the chargingposition. If this is not done, there is danger of damaging theelectrodes by a shifting of the furnace charge.

Rocking range control mechanism As heretofore described, the rockingrange or angle of rock of the melting chamber may be controlled byvarying the position of arm 48 so that the leg ill is moved more closelyor further away from the cam 42. This movement of the arm 48 iscontrolled by a cam 61 which is provided with a cam surface 88. The camsurface 88 is increasingly spaced from the center of rotation of thecam. Associated with the cam surface is a cam roller 69' which isrotatably mounted at the outer end of leg 52 of the arm 48. It willtherefore be evident that movement of the cam will cause a clockwiserotation of the arm 44 and that the amount of this rotation will bedependent upon the pitch of the cam surface 68. By varying the pitch ofthe cam surface, it is possible to increase the rocking angle at anydesired rate. In other words, a small rocking angle maybe provided atthe beginning of the melting operation and large increases of rockingangle may be provided as the end of the melting operation is approached.The pitch of the cam surface 44 should be such as to increase therocking angle at such a rate as to give the best results.

While movement of the cam BI will cause the rocking angle to beprogressiveiyincreased, if

desired, a constant rocking angle may be had at any desired value bysetting the cam 41 at its position to give that rocking angle. 80 longas the cam remains stationary at this position, the melting chamber willcontinue to rock at the angle corresponding to this position.

In order to automatically prevent movement of the cam 81 past itsmaximum rock position, the leg of arm 48 is provided at its outermostend with a plunger 89 which is mounted for axial movement in the end ofthe leg 51. One end of the plunger 59 is threaded to receive a not IIIwhich is disposed on one side oi the leg M. The other end of the plungeris provided with a head portion H which is disposed on the opposite sideof the leg 5]. An expansion spring 12 is disposed between the head H andthe associated surface of the leg, this spring operating to move theplunger head away from the leg until time out ill engages the oppositeside thereof. The head "ll is ar ranged to engage an operating element73 oi control switch H which is secured as hy screws "l5 in suchposition that the operating element l3 will be in the path of movementof the head H. The switch 14 is in the control circuit of a timing motorfor driving the cam 51, as will hereinafter be explained in detail. Itmay, however, be stated at this time that, when. tire cam 51 moved. toits position oi. maxim the l ad which projects on one side of the cam toform a trunnion 16, this trunnion being fitted with a bearing sleeve llthat is supported within a bearing 18. The bearing 18 is supported inthe par tition wall 19 which separates the cam compartment 4| from thegear compartment 80, this latter compartment being arranged to be filledwith a suitable lubricant for the gears.

The other end of the cam hub extends through the forward wall of thehousing as shown at 8! and is provided with a cup-shaped member 82having a radially projecting actuating handle 83 as shown in Figure 6.Within the housing be tween the member 82 and the cam 61, the hub isprovided with an annular flange 84' having a lateral face upon whichthere is secured a lining member 85. The lining member is adapted tomake surface engagement with a cooperatively associated surface 86formed in the wall of the housing.

The bearing sleeve I1 at the other end of the hub is fixedly supportedin a socket I1 and in the bearing 18. This socket contains an expansionspring 88 which is arranged at one end to engage a ring-shaped plate 89and at its other end to engage an anti-friction bearing member 90 whichis seated in the bottom end of the socket. The spring 88 operatestoforce the lining member 85 against the cooperatively associated surface44, these latter members forming a thrust bearing and operating toprovide sufhcient friction to normally retain the cam 61 againstmovement, but permit ready adjustment thereof by means of the handle 83.It will therefore be evident that by placing the handle 83 on one of therocking angle indicating indicia such as 84, in this instance thenumeral indicating a twenty-degree rock, the cam 61 will be in suchposition as to cause the melting chamber to rock at an angle of 20degrees. In the same manner the handle The fill integrally formed tohave a huh iii 88 may be disposed on once! the other numerals to securewhatever rock is desired.

Selector and timing mechanism Extending through the hub of the cam 81 isa shaft 9| which is free for rotatlve movement relative to the hub ofthe cam. One end of this shaft is extended through the bearing 18 andhas mounted thereon a plurality of gears 92, 93, 94, 95, 96, and 91,these gears being respectively provided with 22, 36, 50, 64, 80, and 96teeth. These gears are fixedly secured to the shaft 9| for rotationtherewith.

Adjacent the rear face of gear 91, the back of the housing is formed todefine a socket or well 98 in which there is mounted an expansion spring99. One end of this spring surrounds the projecting end of shaft 9| andbears against the gear 91, whereas the other end of this spring issupported in the bottom of the socket by an antifriction bearing I00.

The other end of shaft 9I extends through the cup-shaped member 82 andhas secured thereto an adjusting knob IOI which is also cupshaped andhas its open end extending over the open end of cup-shaped member 82.The adjusting knob IOI has a central hub portion I02 which is mountedover a contracted end portion I03 of shaft 9| and held in abuttingengagement with a shoulder I04 formed on the shaft by the contractedportion by means of a screw I05 in the shaft end.

The knob IN is provided with diametrically opposed windows I06 and I01through which an indicia bearing dial plate I08, which is mounted on therim of cup-shaped member 82, is visible.

A lost motion connection is provided between the knob IN and member 82.For this purpose, the member 82 is provided on its outer surface with apair of angularly spaced abutment lugs I09 and H0. These lugs definelimit stops between which a lug III on the interior of knob IOI may bemoved. In order to permit ,removal of the knob from the shaft 9|, whenthe screw I05 is removed, the dial plate I08 is provided with aperipheral notch II2 for the passage of lug II I.

Referring to Figure 6, it will be observed that the dial plate I08 isprovided on its face with a triple dial having a plurality of angularlyspaced numerals in concentric relationship which may be brought intoview through the windows I06 and I01, when the knob IN is rotatedbetween the stops I09 and H relative to member 82.

Referring to Figure 2, it will be noted that the top of window I06 hasdisposed thereover the numerals 3--21, and that above window I01 thenumerals 4-5-6 are disposed. These numerals are outwardly spaced fromthe center of rotation of the knob IOI so as to be movable over therespective numerals of the three concentric dials on the plate I00. Thepurpose of the numerals on the knob and numerals on the dfil plate willbe more fully explained subsequently.

The timing mechanism is driven from a small motor II3, as shown inFigure 5, which is connected to a reduced speed shaft II4. through aworm and gear generally indicated at II5. In practice, it has been foundthat a single phase motor of relatively low horse power and speed of1500 R. P. M. works very satisfactorily. The worm and worm wheelconnection I I5 is arranged to reduce the motor shaft speed of 1500 R.P. M.

to a speed of 2% R. P. M. at the reduced speed shaft II4.

Rotatably mounted in the back wall of the main control housing is ashaft II6 which is supported adjacent one end in an anti-frictionbearing H1 and at its other end by an enlarged end portion II8 which isin surface engagement with the interior of a bore I I9 extending throughthe supporting portion of the housing. The antifriction bearing II1 alsoserves as a thrust bearing for the shaft H6.

The shaft H4 is connected to shaft II6 by means of a spring coupling.For this purpose, the shaft II4 has secured thereto a collar I20, andshaft II6 has a collar I2I thereon. These collars are respectivelyprovided with anchor posts I22 and I23 to which the respective ends of acoil spring I24 are secured, the coil spring being disposed around theadjacent ends of the collars.

This arrangement of coupling enables the motor II3 to be started underlight load conditions before the load of the timing mechanism is imposedthereon.

The shaft II6 is provided with a worm I25 which meshes with a worm wheelI26, as shown in Figure 3. The worm I25 has a speed of 2% R. P. M. andthe ratio between this worm and wheel is 32 to 1.

The worm wheel I26 is secured at one end of a pinion shaft I21 by meansof a nut I28. This shaft is rotatably mounted in an anti-frictionbearing I29 supported on the rear wall of the housing. The pinion shaftI21 is provided with fifteen elongated teeth and is slidably supportedat its forward end in a rotatably mounted sleeve I30. This sleeveislongitudinally movable within a bore portion of a housing I3I and anextension bearing sleeve I32. The bore I9I and interior of the bearingsleeve I32 are in registration.

The forward end of the sleeve I30 is provided with an extension memberI33 of circular construction, one end of this member being contracted atI34 for insertion into the end of sleeve I30. The opposite end of memberI33 is likewise contracted as shown at I35 and has rigidly securedthereto a digitally operable handle I36 having a skirt portion I31extending over the member I33 and in telescopic relation with thebearing sleeve I32. By manipulating the handle I36 the sleeve I30 may beeither rotated or longitudinally shifted to positions determined by aplurality of dwell points. These dwell points are determined by spacedcircumferentially extending grooves I38 in the outer surface of thesleeve I30. Cooperatively associated with the grooves is a spring detentball I39, this ball being disposed in an open-ended bore I40 of thehousing, this bore communicating with bore I3I and being disposed atright angles thereto. An expansion spring MI is disposed in the bore I40and hasone endengaging the ball I39 and its other end engaging an endplug I42 in the outer end of the bore.

The innermost end of the sleeve I30 has secured thereto a rightangularly disposed bracket I43 which rotatably supports on oppositesides of the sleeve, gears I44 and I45.

As shown in Figure 3, the gear I45 is rearwardly offset relative to gearI44. Both of these gears mesh with the pinion I21 at all times,regardless of whether the gears are shifted axially along the pinionshaft by the manipulation of selector handle I36 or rotated relativethereto.

From the foregoing it will be appreciated that the gears I44 and I48 mayalternately be brought into engagement with gears 82 to 81 inclusivesimply by rotating the handle I88 in a clockwise or counterclockwisedirection, providing the sleeve I88 has been longitudinally shifted tobe removably retained in the proper dwell position, depending upon whichgear it is desired to make a connection with. This arrangement providesa selective means for securing a variety of driving speeds for the cam81.

In order that the operator may be assured that the handle I88 is beingproperly disposed to give a desired speed, the handle III has an arcuatelatching member associated therewith, whereby the handle I88 may belatched in predetermined positions of rotation and longitudinal shiftingof the sleeve I88.

The latch member I48 has a plurality of notches disposed at differentlevels so that when the handle is shifted in a counter-clockwisedirection, a projecting portion I41 of the handle will first engage anotch I48, then by pulling the handle outwardly and rotating it furtherit may be disposed in notch I48 at a different level, and likewise in anotch I88 at still a diflerent level. In a similar manner the handle I88may be moved from the "oil" position in a clockwise direction fordisposition in notches I8I, I82, and I58.

From the foregoing, it will be apparent that if the handle I88 in the"of!" position is pulled outwardly to the position shown in Figure 3,and then rotated so that the projection I41 is disposed in notch I88,the gear I44 will make connection with gear 82 to give the highestdriving speed. If the handle I88 is now moved in the opposite directionso as to bring the projection I41 into notch III. the gear I44 isdisengaged from gear 92 and gear I45 is brought into engagement withgear 88, which is the next slowest speed of drive. It is thereforepossible for the operator to select a plurality of different drivingspeeds depending upon the position to which the selector handle I88 ismoved. As shown in Figure 2, the various selective positions of theselector handle I88 are represented by indicia as shown at I84, whereinthe various numerals indicate the relative speeds at the respectivepositions of the selector handle.

Manually operable switch control Referring to Figure 2, it will be notedthat there is incorporated with the main control unit at the right endthereof a single pole double throw switch I88 which may be actuated toon" or "of!" positions for rendering the automatic rocking controlmechanism operative and non-operative as desired.

The main control unit is also arranged to removably have disposedthereon a portable push button control switch I58 having forward andreversing push. buttons I81 and I88 respectively. This switch isconnected at the end of a length of flexible cable I89 so that thefurnace operator may carry the switch in his hand and move about thefurnace when manually controlling the same, as during the charging andpouring operation.

Auxiliary rocking control mechanism The auxiliary control consists of anarcuate cam member I88 which is mounted on an end of the meltingchamber. Each end of this cam member is provided with an initiallyengageable cam surface I8I and a surface I82 which is disposed at agreater radius from the center of rotation of the chamber than thesurface Iii, and

which will be engaged after the initial engagement of surface I8I, whenthe melting chamber is further rotated. cooperatively associated withthe cam I88 is a limit switch control mechanism, generally indicated atI88.

As shown in Figure 9, the limit switch mechanism is mounted in asuitable housing I88 which has a removable cover member I88 securedthereto as by a bolt I81.

Extending rearwardly from the housing I88, there is provided a tubularbore portion I88 in which there is rotatably mounted a shaft I88 inanti-friction bearings I18 and "I. This shaft has secured to itsoutermost end an arm I12 in which there is mounted a roller I18. Thelimit switch mechanism is mounted on the furnace base structure by meansof a bracket arm I14 which supports the device in such position that theroller I18 will be in the line of travel of the cam member I88 and maybe engaged by the ends thereof.

The arm I12 is normally held in vertically disposed position by means ofa tension spring I18 which opposes movement of the arm I12 from itsnormal vertical position, and operates to restore the arm to thisposition when it has been moved in either direction therefrom. Thespring I15 is connected at one end to an arm I18 which is keyed to theshaft I69. The other end of this spring is connected to a leg I11 of anL-shaped rocker arm I18, this rocker arm being pivotally mounted forrotative movement on a pivot member I19. The other leg I88 of the rockerarm is provided at its outer end with a roller I8I which is adapted toengage a dwell recess I82 in a double cam I88, this cam being keyed toshaft I89. On each side of the dwell recess I82, are similarly disposedcam surfaces I84 and I85.

When the roller I8I is disposed in the dwell recess I82, the arm I12 isin normal vertically disposed position, but should the arm I12 berotated in either direction from its normal position, the roller I8Iwill correspondingly move onto cam surface I84 or I85, and the arm I18'will be moved from its normal position to increase the tension ofspring I15. It will therefore be evident that the spring I15 having beenadditionally tensioned will tend to restore the roller I8I to the dwellrecess I82 and move the arm I12 to normal position.

In addition to the cam I83, the shaft I89 has fixedly secured thereto apair of cams, namely, I88 and I81. These latter cams have correspondingcam surfaces I 88 and I89 respectively, the centers of these camsurfaces being angularly spaced at substantially sixty degrees. In thenormal position of the arm I12, the center line of cam surface I89 isdisposed so as to pass through the center of a cylindrical cam followerI98 which is carried on a spring strip I9I, this spring strip beinganchored at its opposite end on a support I92 which is integrally formedwith the housing of the limit switch. The cam surface I89, acts todeflect the spring strip I 9| to close a switch I93 through an actuatingbutton I94. This switch is normally open, but is malntained closed solong as the cam follower I98 is in contact with cam surface I89.

The cam surfaces I84 and I 88 are so disposed relative to cam I81 that,if the arm I12 is rotated substantially twenty degrees on either side ofnormal position, one of these surfaces will come into contact with a camfollower. For example, if the arm I 12 is moved substantially twentydegrees in a counter-clockwise direction, 78

then the cam surface I88 will engage and deilect a spring strip I95which is operative to actuat'e a normally closed switch I98. On theother hand, if arm I12 is moved substantially twenty degrees in aclockwise direction, the cam surface I84 will engage a cam follower anddefleet spring strip I91 to actuate a normally open switch I98.

It will be observed that during the actuation of switches I96 and I98,theswitch I93 continues to remain closed until the lever I12 has beenrotated in either direction substantially a total of forty degrees fromnormal position. At this point, the follower I moves off the cam surfaceI89, thereby enabling switch-I93 to open its contact. As soon as the camI60 disengages the roller I13, the spring I15 acts inthe mannerpreviously described to restore the cam mechanism to its normalposition, wherein switch I93 is again closed. The spring strips I95 andI9! are mounted in a similar manner to spring strip I9I.

The initial movement of twenty degrees -in either direction is obtainedby one of the end cam surfaces I6I of cam I60 engaging the roller I13,whereas the additional twenty-degree movement is accomplished when thecam surface I62 of cam I60 engages the roller I13. The limit switch isso wired into the control circuit that actuation of switches I96 and I98operate to reverse the rotation of the melting chamber, whereas theoperation of switch I93 functions to cause the melting chamber rotationto cease. This will be more fully explained subsequently.

Operation The main power circuit for the furnace driving motor, in thiscase three phase sixty cycles, as indicated at I99, is brought inthrough main manually operable disconnecting switches 200 and thence toa three pole main or safety contactor 20I having an operating coil 202.From this contactor, the power circuit is connected to a forwardcontactor 203 having an operating coil 204, and a reversing three polecontactor 205 having an operating coil 206. The reversing contactor hasan additional interlocking contact 201. The outlet circuit from theforward and reversing contactors feed the rocking motor I8 and thesecontactors may be selectively actuated to run this motor either in aforward or reverse direction depending upon which contactor is closed.

The control circuit is fed from one phase of the power circuit throughconductors 208 and 209 to a manually operable double pole single throwswitch 2I0. This switch operates to connect the control circuit to acontrol transformer 2I I.

Assuming that it is desired to automatically control the rock of themelting chamber, the automatic rock switch I55 is moved into contactwith contact 2I2, which is the on position of the switch. If the maincontrol switch 2I0 is now closed, the safety contactor 20I is closed byits operating coil 202 becoming energized through the following circuit:From one side of the secondary of the control transformer 2 through fuse2l3, conductor 2I4, conductor 2I5, through the closed contacts of switchI93, conductor 2I6, conductor 2" to one side of operating coil 202, fromthe other side of this coil to conductor 2I8 and thence throughconductor 2I9 to the other side of the secondary of the controltransformer.

Simultaneously with the closing of switch 2I0, the timing motor H3 isenergized through the following circuit: From one side of controltransformer 2 through fuse 2I3, conductor 2, conductor 220 throughswitch I65 to its contact 2I2, through conductor 22I, conductor 222,through the contacts of switch 14, conductor 223 to one side of thetiming motor, from the other side of the timing motor through conductor224, thence through conductor 2I9 to the other side of the secondary ofthe control transformer 2I I. The timing motor therefore having beenstarted will rotate members MI, and if the lug III thereon is inengagement with the lug I09 of member 82, then the cam 61 willimmediately start moving to increase the rocking angle in accordancewith the pitch of its cam surface.

Also when the switch 2I0 is closed, assuming that the melting furnace isin such position that neither the forward or reverse contactors 203 or205 have been closed, then a control relay 225 determines the directionin which the furnace will initially rotate. This relay has an operatingcoil 226 and is arranged with normally closed contacts 221 which areclosed when the operating coil is de-energized, and contacts 228 whichwill be closed when the operating coil 226 is energized. The operatingcoil 226 being deenergized, contacts 221 are closed, and the forwardcontactor 203 will close its contact by virtue of its operating coil 204being energized through the following circuit: From one side of thesecondary coil of control transformer 2I I, through fuse 2I3, conductor2, conductor 220, through switch I55 to its contact 2I2, thence throughconductor 22I, through contact 221 of relay 225, conductor 229,conductor 230, through the normally closed contacts of .push buttoncontrol switch I58, thence through conductor 23I, to one side ofoperating coil 204, thence through conductor 232, conductor 2I8, andthence through conductor 2I9 to the other side of the controltransformer secondary. As soon as the forward contactor 203 closes, thedriving motor I8 starts rotating the furnace chamber in the forwarddirection and at the same time will operate to rotate cam 42 in the samedirection that the furnace is operating.

It will be seen that as the cam 61 continues to move the rocking angleis gradually increased due to the fact that arm 48 is being rotated in aclockwise direction about its pivot, thereby moving the switches 53 and54 away from the cam so that it will necessitate greater rockingmovement of the cam 42 in order to actuate these switches.

When the cam 42 has moved in a forward direction a distance dependingupon the amount of movement which has transpired of cam 61, the cam 42operates to close switch 53. Closing switch 53 will energize the controlrelay 225 through the following circuit: From one side of the secondaryof the control transformer 2, through conductor 2, conductor 220, to themovable blade of switch I55, thence through conductor 233 to thecontacts of switch 53, conductor 234, through the contacts of switch 54,conductor 235, operating coil 226 of relay 225, thence through conductor236 to conductor 2I8, thence through conductor 2I9 to the other side ofthe control transformer secondary.

Since the operating coil of the forward contactor 203 is fed through thenormally closed contacts 221 of relay 225, energization of this relaywill cause the contacts 221 to open and deenergize the coil of theforward contactor, whereupon this contactor will open.

The control relay 225 then closes its normally open contacts 220 withthe result that the reverse contactor 205 is closed by virtue of itsoperating coil 209 being energized through the following circuit: Fromone side of the secondary of the control transformer 2I I, throughconductor 2I4, conductor 220, switch I55 to its contact 2I2, conductor22I, through contacts 228 of control relay 225, thence through conductor231 to the normally closed contacts of push button control switch I51,through conductor 229 to one side of coil 205, thence through conductors229 to conductor 2l9, thence through conductor 2I9 to the otherside ofthe secondary of the control transformer 2.

As soon as the reversing contactor 205 closes its contacts, the motor I8reverses its direction of movement to drive the melting chamber in thereverse direction.

Of course, with the melting chamber moving in the reverse direction, thecam 42 will also reverse its direction of movement and switch 52 willopen its contact, but will not trip out the reversing contactor, for thereason that when this contactor closed, its interlocking contact 201closed an interlocking feed circuit around switch 52. This circuit is asfollows: From one side of control transformer 2I I, through fuse 2I2,conductor 240, through interlocking contact 201, conductor 2, throughthe contacts of switch I95, conductor 242, conductor 224, contacts ofswitch 54, conductor 235, through operating coll 225 of relay 225,conductor 285, conductor 2I9, conductor 2I9 and thence to the other sideof the secondary of control transformer 2. The operating coil of relay225 therefore remains energized and keeps contacts 220 thereof closed.whereby the coil 205 remains energized.

As soon as the reverse movement of the melting chamber has beensufllcient to cause cam 42 to open switch 54, the control coil 22B ofrelay 225 becomes de-energized with the result that its contacts 229 areopened and its contacts 221 are closed.

Action of the relay will open the energizing circuit of operating coil205 of the reversing contactor, whereupon this contactor trips open.Moreover, the circuit is now established with the forward contactorwhich now closes and connects the driving motor so as to drive themelting chamber in a forward direction.

The rocking of the furnace chamber continues in alternate directionswith gradually increasing angle of rock, due to the action of cam 51.When cam surface I60 engages the roller I19 in either movement of themelting chamber, the limit switch control then comes into operation.

Assuming that the melting chamber is being moved in forward direction,the forward contactor 203 being closed. the engagement of cam surfaceIBI with roller I13 will operate to close the contacts of switch I98.Closing of this switch will energize the operating coil of relay 225through the following circuit: From one side of the secondary of thecontrol transformer 2, through fuse 2 I3, conductor 2I4, through thecontacts of switch I98, conductor 234, the contacts of switch 54,conductor 235 to operating coil 226, from this coil through conductor296 to conductor H0, and thence through conductor 2I9 to the other sideof the secondary of the control transformer. The control relay 225 nowbeing enersized picks up, breaking its contacts 221 to trip out theforward contactor and close contacts 229 which energize the operatingcoil of the reverse contactor 205 as previously explained.

Immediately upon the closing of the reverse contactor, the interlockingcontact operates as previously explained to interlock the energizingcircuit of operating coil 229 of relay 225 through limit switch I95.

The rocking motor I therefore reverses its direction of rotation anddrives the melting chamber in reverse direction until the cam surface.

I6I at the other end of cam I50 contacts with roller I13. Movement ofthe cam under these conditions operates to open limit switch I99 andde-energize the operating coil of relay 225, whereupon contacts 220thereof are opened and contacts 221 closed to energize the forwardcontactor 203 as previously explained. It will therefore be evident thatthe melting chamber will continue to rock at its normal maximum rockwherein the reversals of the driving motor are controlled through thelimit switches.

During the rocking of the melting chamber at full normal rock, the cam61 continues to turn until it reaches the off" position, at which pointit has moved the arm 40 in a clockwise direction as far as possible. Atthis point the arm operates control switch 14 and opens its contacts tostop the timing motor II3, whereupon the cam 41 ceases to advancefurther.

If for any reason during the rocking of the melting chamber, when theswitch I55 is set for automatic rocking control, the chamber should failto reverse at the end of full normal rocking movement and shouldover-travel into the danger' zone, then the cam surface I52 of cam I50further moves the roller I19 to actuate the over-travel switch I93,which opens the supply circuit to the operating coil 202 of the safetycontactor 20I. This safety contactor will therefore open and deenergizethe driving motor I5 and stop the movement of the melting chamber.

Since the over-travel switch has a tendency to open and is held closedby the action of spring I! and spring I15; it will be apparent that ifthese springs should fail the safety switch would be opened to stop theoperation of the furnace. In other words, normal operation cannot beaccomplished unless the over-travel switch is in perfect condition.Moreover, due to the manner in which the safety switch is connected intothe system, it is operated only occasionally, with the result that thereis little likelihood of its getting out of order, and its reliability asa safety feature is materially increased.

At the conclusion of the normal rocking cycle, the control switch I55should be thrown into engagement with its contact 243, which is the offposition.

With the automatic control switch in off position, the control of theforward and reversing contactors istransferred to push button controlswitches I51 and I55, and since these switches are in the normally oif"position, the forward and reverse contactors will be opened to stop themotor I8 and discontinue the rocking movement of the melting chamber.

With the automatic control switch in 011" position. the safety contactoris closed by virtue of its operating coil 202 being energized throughthe following circuit: From one side of the secondary of the controltransformer, to fuse 2II, conductor 2, conductor 220, to switch I55,from its contact 243, through conductor 244, conductor 2" to one side ofcoil 202, thence through conaromas ductors 2I8 and M9 to the other sideof the. secondary of the control transformer.

Although the manually operable push button controls I51 and I58 areutilized during the charging and pouring operations, these controls maybe used in emergency conditions for operating the furnace during theautomatic rocking thereof. The push button controls may be used tooperate the furnace in either forward or reverse direction withoutinterfering in any way with the automatic control of the furnace, and assoon as the manual operation is suspended, the furnace willautomatically return to automatic operation and continue with therocking cycle.

For manually controlling the rocking of the furnace melting chamber,control push button I5! is depressed until its normally open contactsare closed, whereupon the forward contactor203 is closed by energizingits operating coil through the following circuit: From one side of thecontrol transformer, through fuse 2I3, conductor 2 I 4, conductor 220,conductor 245, the contacts of push button I51, conductor 246, conductor230,

the normally closed contacts of push button I58, conductor 2 3I to onesideof coil 204, from the other side of this coil through conductor 232,conductor 2I8, and thence through conductor 2I8 to the other side of thecontrol transformer. It will be apparent that the forward contactor willremain closed and operate the furnace rocking motorin forward directiononly so long as the push button is kept depressed. As soon as the pushbutton is released, the forward contactor opens to de-energize thedriving motor I8.

. Reverse movement of the melting chamber is secured by depressing thepush button I58 until its normally-open contacts are bridged, whereuponthe reversing contactor closes by virtue of its operating coil beingenergized through the following circuit: From one side of the secondaryof the control transformer, through fuse 2 I3, conductor 2I4, conductor220, conductor 24! through the contacts of push button I58, conductor248, through the normally closed contacts of push button I51, thencethrough conductor 238 to one side of coil 206, through the other side ofthis coil through conductor 23!! to conductor H8, and thence throughthis conductor to conductor 2I8 and the other side of the secondary ofthe control transformer. As in the case of the forward push buttoncontrol, likewise the reverse push button control will operate therocking motor I8 in reverse direction only so long as the push buttonI58 is depressed, and that when this-push button is released, thereversing contactor drops open to stop the motor.

In connection with the use of the push button controls I 51 and I58, itshould be noted that since the pouring range is outside the safe rockingrange of the melting chamber, in which case the over-travel switch isheld open, the push button control will operate at this time only whenthe automatic rock control switch I55 is in the off position.

It will be evident from the foregoing description of the automatic andmanual push'button control that if a rocking center is chosen tocorrespond to a charging position either forwardly or to the rear of avertical central position of the melting chamber, the cam control bymeans of cam I60 will come into operation when the melting chamber isrocked in one direction sooner than when it is rocked in the otherdirection. Under these conditions, the limit switch will continue tolimit the rocking in the one direction,

whereas the rock in the opposite direction willcontinue to be controlledby the action of cams 42 and 81 until the maximum rocking limit in theopposite direction is reached.

In-Figure 12, clutches 248 and 250 have been diagrammatically shown soas to respectively permit adjustment of the rocking center index arm 46and the rocking angle adjustment lever 83.

When it is desired to operate on a rocking cycle having an initialconstant rocking period for a predetermined interval before theautomatic increase of rock begins, this is accomplished by adjustingthelost motion connection between members 82 and II". For this purpose theadjusting lever 83 would be set on the constant angle of rock desired,and member IN is rotated in a counterclockwise direction so that the lugIII is moved in a counter-clockwise direction so as to be disposed atsome point between the lugs I09 and H0, depending upon the time intervalindicated on the dial I08. It will therefore be apparent that member IOIwill'have to be moved a predetermined distance before it strikes the lugI09 and starts movement of member 82 and cam 81 to begin the increase ofthe rocking angle. This will be more clearly understood in the examplesof rocking cycles to be explained later.

Illustrative rocking cycles The nameplate as shown in Figure 2 tabulatesthe approximate time in minutes required to reach' full rock fromvarious starting positions. The extreme left-hand column shows numeralsfrom 1 to 6 which correspond to those on the selector notches, andindicate the relative speeds at which the timing motor will drive thecam 61. The three left-hand columns under the words Front or Rear showthe approximate time interval when the charging door is started welldown in the front or rear positions. The indicia heading these columns,namely, 20, 40, and 60, indicate the setting of the range lever 83 onthe range dial 84 at the start; that is, the angle of rock at the start.The three right-hand columns show similar indicia for positions of thecharging door at the top center of the melting chamber. I

For example, when the melting chamber is charged with the door at topcenter and the startingrocking angle is 40, then with the selector setin number 3 notch, 18 minutes are required to bring the furnace up tofull normal rock. This 18-minute interval is the period of increase ofthe rocking angle and does not include any delaying which may be addedwith the constant rocking period knob.

The afore-mentioned table is provided 'to give comparative values as abasis for arriving at the rocking cycle which is most suitable for anyparticular charge of metal.

In Figure 13, there is graphically represented the minimum and maximumlength of rocking cycles which may be attained with the controldescribed herein.

Curve M is secured when the rocking cycle is started with the doorat topcenter of the safe rocking range, the selector handle I36 being set innotch No. 1 and the rocking range lever 83 being set for a rocking angleof 60. The words Automatic increase should appear in the windows I06 andI01. Under these conditions the melting chamber will begin rocking at anangle of 60 and will increase to maximum rock in approximately sixminutes.

As shown by curve N, i! the door is at the top center, the selector onNo. 1 notch, and the starting rock at 20, the maximum rock angle will bereached in substantially 11 minutes.

On the other hand, it instead of having the charging door at the topcenter, the door is for example 10 above the limit of sale rock, that iswell forward or well to the rear, then with the selector on No. l notchand the starting rock at 20, the maximum rocking angle will be reachedin approximately minutes, as shown by the curve "0".

In the case of the three curves mentioned above, the selector was placedin No. 1 notch, which is the fastest speed of the cam 61.

Curve P shows the rocking cycle when the charging door is started at thetop center of safe rocking range, the selector being placed on No. 6notch, this being the slowest speed of drive for the cam 61, a 25-minuteinitial constant rock of at the start. The constant rocking angle of 20for minutes is set by adiusting the rocking range lever 03 so that itwill be at the 20-degree indication and then rotating the constantrocking period knob l0l until the numeral 25 appears in the-"window I01under the numeral 6 above the window.

With this setting as shown by curve P it will be observed that themelting chamber will rock continuously at a 20-degree angle for 25minutes and at this point will begin to increase the rocking angle andreach a maximum in approximately 76 minutes from the beginning of the'rocking cycle or 51 minutes irom the termination or the constantrocking period.

Curve Q represents a similar setting to that used for curve P, exceptthat instead of starting the charging door at the top center of saferocking range, the door in this caseis started well to the front orrear, for example 10 above the limit of safe rock. In this case, themelting chamber will rock at a constant angle for approximately 25minutes at the end or which time it will begin increasing the rockingangle and reach a maximum at substantially 68 minutes from the end ofthe constant rocking period or a total of 93 minutes from the beginningof the rocking cycle.

The curves M, N, 0, P, and Q graphically represent the maximum andminimum length of rocking cycles, and it will be apparent that byvarying the selector setting, the setting of the rocking range lever 83and the setting of the constant rocking period knob l0l, it is possibleto secure substantially any desired rocking cycles between the limits asshown by the above curves.

From the foregoing description it will be apparent that the hereindescribed invention provides a selective control mechanism which willenable adjustment of the constant and variable characteristics of thevarious elements of the rocking cycle to give a desired cycle of rockingoperation; which will permit a pre-setting oi the control mechanism sothat once the rocking is started, the predetermined cycle will beautomatically carried out; which embodies novel protective controlfeatures for guarding against abnormal conditions of operation whichwould cause the melting chamber to travel in a forward or reversedirection past the safe maximum angle of rock limit; which includesimproved means for controlling the rate of increase of the rockingangle; which includes novel manual push button control for augmentingthe automatic control mechanism and for jogging the furnace during thecharging or pouring operations; which includes improved means forindicating the center of the rocking cycle; which provides improvedcontrol mechanism for automatically controlling the amount of increaseof the rocking angle; control equipment including novel limit switchmeans for reversing operations on initial movement and for stoppingfurther rocking oi the melting chamber upon further or over-travelmovement of the chamber; and which includes automatic means whereby themelting chamber may be initially rocked through a selectable constantrocking angle for a pre-determined period oi time, after which the angleof rock will be progressively increased for a subsequent predeterminedperiod of time at a varying rate of rock.

Now, of course, it is to be understood that while the invention isillustrated and described in detail in its preferred form, the inventionis not to be thus limited, but only insofar as defined by the scope andspirit of the appended claims.

We claim as our invention;

1. In a device of the character described including a chamber mountedfor rocking movement, power means for driving said chamber, means havingparts responsive to the movement of said chamber for reversing itsdirection of movement, and timing means for varying the time intervalbetween said reversals at a predetermined rate.

2. In a device of the character described including a chamber mountedfor rocking movement, power means for driving said chamber, means havingparts responsive to the movement of the chamber for reversing itsdirection of movement, adjustable means associated with said partswhereby the interval between reversals may be increased and decreased,and timing means for varying said adjustment according to apredetermined rate.

3. In a device of the character described in cluding a chamber mountedfor rocking movement, power means for driving said chamber, switch meansresponsive to the movement of said chamber for alternately reversing itsdirection of movement, and timing means for retarding the actuation ofsaid switches at a predetermined rate.

4. In a device of the character described including a chamber arrangedfor rocking movement between predetermined maximum and minimum limits,means including a timing mechanism for alternately reversing thedirection or movement of said chamber and progressively increasing theamount of rock from said minimum to said maximum at a predeterminedrate.

5. In a furnace of the character described including a metal meltingchamber arranged for rocking movement between predetermined maximum andminimum limits, means for alternately reversing the direction ofmovement of said chamber, and timing means for increasing the angle ofrock defined by said points of reversal at a rate corresponding to therate at which the metal is being melted.

6. In a device of the character described a chamber mounted for rockingmovement, power means for driving said chamber, means for alternatelyreversing the direction of movement of the chamber and progressivelyincreasing the angle of rock, at a predetermined rate, said meanscomprising a member movable in accordance with the movement of saidchamber, control contacts alternately actuated in response to themovement of said member, and means for varying the time interval betweenthe successive actuations of said contacts by the member.

7. In a device of the character described a chamber mounted for rockingmovement, power means for driving said chamber, means for alternatelyreversing the direction of movement of the chamber and progressivelyincreasing the angle of rock at a predetermined rate, said meanscomprising a cam member rotatable in accordance with the movement ofsaid chamber, and control contacts alternately actuatable .by said camin response to its movement, said contacts being mounted for movementtowards and away from said cam surface, whereby the time intervalsbetween the actuations of said contacts may be varied.

8. In a device of the character described a chamber mounted for rockingmovement, power means for driving said chamber, means for alternatelyreversing the direction of movement of the chamber and progressivelyincreasing the angle of rock at a predetermined rate, said meanscomprising a cam member rotatable in accordance with -..the movement ofsaid chamber, control contacts alternately actuatablc by said cam inresponse to its movement, said contacts being mounted for movementstowards and away from said cam surface, whereby the time intervalsbetween the actuations of said contacts may be varied, and means formoving said contacts away from the cam surface with an increasing speed.

.9. In a device of the character described a chamber mounted for rockingmovement, power means for driving said chamber, means for alternatelyreversing the direction of movement of the chamber and progressivelyincreasing the angle of rock at a predetermined rate, said meanscomprising a cam member rotatable in accordance with the movement ofsaid chamber, control contacts alternately actuated by said cam inresponse to its movement, said contacts being mounted for movementtowards and away from said cam surface, whereby the time intervalsbetween the actuations of said contacts may be varied, means for movingsaid contacts as a unit, and means adjustable to vary the speed ofmovement of said contacts.

10. In a device of the character described having a chamber mounted forrocking movement; means for progressively increasing the angle of rockof said chamber from a minimum to a predetermined maximum value inincreasing increments, said means comprising a member rotatable inaccordance with the rocking movement of said chamber, contactsalternately actuated by said member when it is moved in oppositedirections, means for moving said contacts to vary the time intervalbetween the actuations of the contacts, and cam means for moving saidcontacts with increasing speed.

11. In a device of the character described having a chamber mounted forrocking movement; means for progressively increasing the angle of rockof said chamber from a minimum to a predetermined maximum value inincreasing increments, said means comprising a member rotatable inaccordance with the rocking movement of said chamber, contactsalternately actuated by said member when it is moved in oppositedirections, means for moving said contacts to vary the time intervalbetween the actuations of said contacts, cam means for moving saidcontacts with increasing speed, and means adjustable to drive said camat different speeds, whereby the time interval of the rocking cycle forminimum to maximum rock may be varied.

12. In a device 'of the character described a chamber mounted forrocking movement, power means for driving said chamber, and controlmeans operable to vary the angle of rock and the rate of change of saidangle during a predetermined period of time, said means comprising asubstantially heart shaped cam surface rotated in forward and reversedirection concurrently with the movement of said chamber, a pivot arm, apair of spaced switches on said arm alternately actuated by said camsurface, and a second cam acting upon said arm, whereby the arm may bemoved in a predetermined manner, to vary the position of said switchesrelative to said first cam surface.

13. In a device of the character described, a chamber arranged forprogressively increasing rocking movement from a predetermined minimumto a maximum angle of rock, means normally controlling the rockingmovement, and auxiliary control means for superseding the first meanswhen the rocking movement of the chamber reaches the maximum angle ofrock.

14. In a device of the character described, a. chamber arranged forprogressively increasing rocking movement from a predetermined minimumto a miximum angle of rock, means normally controlling the rockingmovement, and

auxiliary control means for superseding the first means when the rockingmovement of the chamber reaches the maximum angle of rock, saidauxiliary control means including cam members operated in response tothe movement of the chamber.

15. In a device of the character described, a chamber arranged forrocking movement to predetermined angularly spaced maximum limits,control means arranged to normally rock the chamber in progressivelyincreasing amounts, the mid-point of the normal rocking angles beingangularly disposed from the mid-point of the angle defined by saidmaximum limits, and auxiliary control for superseding the first controlmeans when the movement of the chamber in rocking movement frompredetermined minimum to a maximum limit of safe rock, means normallycontrolling the rocking movement, auxiliary control means forsuperseding the first means when the rocking movement of the chamberreaches the maximum angle of rock, and means for stopping the movementof the chamber when the maximum angle of rock is exceeded.

17. In a device of the character described, a chamber arranged forprogressively increasing rocking movement from a predetermined minimumto a maximum angle of rock, means normally controlling the rockingmovement, auxiliary control means for superseding the first means whenthe rocking movement of the chamber reaches the maximum angle of rock,and manually operable means controlling the movement of said chamber inlieu of the normal and auxiliary controls.

18. In a device of the character described, a chamber arranged forrocking movement, cam means carried by said chamber defining the maximumsafe rocking angle, a movably mounted member disposed for engagement bysaid means and initially moved thereby when the maximum limit of saferocking in either direction is reached, and further moved when themaximum limit is exceeded, switch means actuated in response to saidinitial movement for reversing the direction of movement of saidchamber, and other switch means operable in response to said furthermovement for stopping the movement of said chamber.

19. In a device of the character described, a chamber arranged forrocking movement, cam means carried by said chamber defining the maximumrocking angle, a movably mounted member disposed for engagement by saidmeans and initially moved thereby when the maximum limit of safe rockingin either direction is reached, and further moved when the maximum limitis exceeded, switch means actuated in response to said initial movementfor reversing the direction of movement of said chamber, other switchmeans operable in response to said further movement for stopping themovement of said chamber, and manually operable jogging control formoving the chamber after the latter switch means has operated.

20. In a device of the character described having a chamber mounted forrocking movement, means for normally controlling the rocking movement ofthe chamber, and means operative to reverse the direction of movement ofthe chamber when it is rocked to predetermined limits, and stop therocking movement when the chamber is moved in either direction past saidlimits, said means comprising a rotatable member, means biasing movementof said member in either direction from a normally disposed position,cam means carried by said'member, a pair of switches respectivelyactuated by said cam means upon an initial movement of said member ineither direction from its normal position, and a switch actuated by saidmember when it is further moved from its normal position in eitherdirection.

21. Control means comprising a rotatably mounted member having a normalposition, means biasing movement of said member in either direction fromits normal position, a cam carried by said member, a switch actuated bysaid cam when the member is slightly moved in one direction from itsnormal position, a second cam carried by said member, a second switchactuated by the latter cam when the member is slightly moved in theopposite direction, a third cam carried by said member, and a thirdswitch actuated by said third cam when the member is additionally movedin either direction.

22. Apparatus of the character described comprising a chamber arrangedfor oscillatory movement, and means for oscillating said chamber insuccessively increasing angles of rocking movement for a predeterminedinterval of time, said means including a rock controlling memberarranged when moved in one direction to cause an increase in the rockingangle of the chamber, a cam surface for moving said member, the amount01 increase of said rock being determined by the slope of said camsurface, and means for driving said cam surface at a predeterminedspeed.

23. Apparatus of the character described comprising a chamber arrangedfor oscillatory movement, means for oscillating said chamber insuccessively increasing angles of rocking movement for a predeterminedinterval of time, said means including a rock controlling memberarranged when moved in one direction to cause an increase in the rockingangle of the chamber, a cam surface for moving said member, the amountof increase of said rock being determined by the slope of said camsurface, and a variable speed drive for the cam surface.

24. Apparatus of the character described comprising a chamber arrangedfor oscillatory movement, means for oscillating said chamber insuccessively increasing angles of rocking movement for a predeterminedinterval of time, said means including a rock controlling memberarranged when moved in one direction to cause an increase in the rockingangle of the chamber, a cam surface for moving said member, the amountof increase of said rock being determined by the slope of said camsurface, means for driving said cam surface at a predetermined speed,and time delay means providing an adjustable time delay before startingthe rocking angle increase.

25. Apparatus of the character described comprising a chamber arrangedfor oscillatory movement, means for oscillating said chamber insuccessively increasing angles of rocking movement for a predeterminedinterval of time, said means including a rock controlling memberarranged when moved in one direction to cause an increase in the rockingangle of the chamber, a cam surface for moving said member, the amountof increase of said rock being determined by the slope of said camsurface, means for driving said cam surface at a predetermined speed,and means responsive to a predetermined movement of the rock controllingmember for rendering the driving means inoperative.

26. In means for controlling the movement of an oscillatably mountedchamber, a cam oscillatably movable with said chamber, a cam followerhaving a cam abutment surface, a switch carried by said cam follower,and a movable switch actuating member projecting past said abutmentsur-- face for normal engagement by said cam, said abutment surfaceacting to limit the movement of said switch actuating member duringabnormal movements of said cam.

27. In means for controlling the movement of an oscillatably mountedchamber, a driving motor, a supply circuit for said motor, reversingswitches energizable to control the direction of rotation of said motor,a switch in the supply circuit of said motor arranged to open whendeenergized, and a limit switch responsive to abnormal movements of saidchamber for deenergizing the switch in the supply circuit, whereby themotor is rendered inoperative.

28. In means for controlling the movement of an oscillatably mountedchamber, a driving motor, a supply circuit for said motor, reversingswitches energizable to control the direction or rtation of said motor,a safety switch in the supply circuit of said motor arranged to openwhen deenergized, a limit switch responsive to abnormal movements ofsaid chamber for deenergizing the safety switch to render the motorinoperative, said limit switch normally tending to open and includingcam actuated spring means for normally maintaining the limit switchclosed.

LEON V. PI'I'I'MAN. CLAUDE M. WEINHEIMER.

